Of the 2,348 miles of streams in Chester County, PADEP periodically assesses 1,394 stream miles using an USEPA-approved assessment methodology to determine if a stream is meeting water quality standards. In the 2020 report, PADEP listed 961 miles of streams in Chester County as impaired, which means they do not meet water quality standards. The list of impaired streams, as well as the list of streams assessed that met the water quality standards, are found in the "2020 Pennsylvania Integrated Water Quality Monitoring and Assessment Report."
Common impairments in Chester County include "siltation due to urban runoff/storm sewers” and "nutrients due to agriculture." In total, there are over two dozen unique impairment categories listed in Chester County. Stream can be listed by PADEP as impaired for two or more reasons if there are multiple impacts that result in the stream not attaining their designated use.
Summary by Major Basins
Chesapeake Bay and Susquehanna River Tributaries: 93% of their stream miles are impaired,
Christina River Basin: 55% impaired
Delaware River Tributaries: 100% impaired
Schuylkill River Tributaries: 67% impaired
Resources for 2020 Impaired Waters
To improve the waters of Chester County, it is essential to understand which streams are impaired and the cause of that impairment. To assist with this, several resources are available here:
CCWRA Interactive Map Gallery (interactive online maps)
The above link directs to a series of interactive maps that contain a variety of information about the County's water resources. Included in these online maps are information on the impairments that are listed by PADEP for the waters in Chester County. The "Water Resources of Chester County Tabbed Viewer" and the "2020 Impaired Waters View by "Cause" Web Map" are the two good tools to start with, although most of the other tools also allow the user to view impaired waters information.
Chester County 2020 Impaired Waters Map series [2020 data] (11x17 .pdf maps)
This series of pdf maps begins with an overview map of all Chester County streams impacted by all causes of impairments, and includes 16 additional maps showing the locations of streams by each different cause of impairment, as well as other related maps.